This invention relates to apparatus for feeding workpieces to and discharging formed articles from a blow molding station.
While the blow molding art goes back over 200 years, it has only been in the last 15 years or so that blow molding of hollow plastic articles has achieved significant commercial success. Recently, techniques have been developed for forming biaxially oriented hollow articles utilizing a method wherein a workpiece such as a preform (i.e. a tubular body of thermoplastic material) is fabricated into an article while at orientation temperature. One such method, is to take the preform as soon as it is formed by the extrusion apparatus and while it is still hot, and transfer it directly to the blow molding apparatus where it is stretched and molded into the desired shape. Another method involves the reheating and blow molding of cold preforms as disclosed for example in Wiley et al., U.S. Pat. No. 3,507,005. Such method has the advantage of separating the formation of the preform from the article forming operation and gives added flexibility to the overall process since the finished product can be prepared at a later time and can even be carried out by others who desire to purchase the preforms and fabricate the finished product at their own facilities. Inherent in such a reheating technique is the necessity for transferring preforms from a heating means to a molding station. In either method, the transfer of the preform to the blow mold can easily be accomplished by hand or mechanical means as shown for example in Harris, U.S. Pat. No. 3,721,514 or Moore, U.S. Pat. No. 3,765,813. Oftentimes, however, the resulting time cycle does not lead to the high production rates desired in a successful commercial operation and one significant limiting factor is the time taken to feed and discharge the preforms into and out of the blow molding station.